[Stoves] stoves and credits again

[Andrew Heggie]

On 21 September 2017 at 18:17, Paul Anderson <psanders at ilstu.edu> wrote:
>
> 1.  Pyrolysis is around the 550 to 650 C range (unless burning very hot with
> much forced air)
> 2.  The char yield is about 20% of the dry weight of the biomass fuel
> (mainly think of wood).
> 3.  That char contains about 30%  (NOT 50%) of the ENERGY of the biomass.

Paul I have had a look at some of the early work on charcoal, I see
graph by Pohl 1970 that show charcoal heated to 600C being composed
90% fixed carbon, now if you ignore the other 10% that contains carbon
hydrogen oxygen and ash and you still have 20% of the original dry
weight then you have 18% of the original dry weight as carbon. So if
you start with dry hardwood at the 18.6MJ/kg Tom Reed allowed for it
and most woody biomass and end up with 0.18 carbon at 33MJ/kg so about
32% in the fixed carbon plus a contribution from the 8% of tars etc.
less the 2-3% ash (more ash from leaves buds straw etc.) So I suspect
you are more right to be at the lower end than the 50% I gave which is
what I remember from charcoal made at lower temperatures for sale in
barbecues.


>
> If writers wish to continue to say 50% of the ENERGY remains in TLUD-type
> charcoal, then let's resolve that here and now.   Otherwise there can  be no
> true discussion about the value of the TLUD char.

Agreed, let's see what figures others have.

Andrew